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APNG (animated PNG) images support [Firefox and Safari 8 support it]

APNG is an extension of the Portable Network Graphics (PNG) format, adding support for animated images. It is intended to be a replacement for simple animated images that have traditionally used the GIF format, while adding support for 24-bit images and 8-bit transparency. APNG is backwards-compatible with PNG; any PNG decoder should be able to ignore the APNG-specific chunks and display a single image.